R129 500SL Stalling
 

Hi all, John here, so I'm trying to get a 2nd opinion here, I've posted on Benzworld with this issue, any help/opinions would be appreciated! . I have a 1991 500SL Ca version 129.066 37K miles, issue I've been having started 7 months ago and now its gotten bad, started with dreaded dash flash and car stalling at rolling stop. I thought issue was low voltage to systems, and it was, had below 12v at idle with any accessories on, so replaced battery and alternator,OVP, all fuses, also replaced dist caps and updated rotors, now have a healthy 13.82V running voltage, but car is stalling big time now. I can crank and no start, all cluster lights are off with key in #2 position?, I can remove key and reinsert a few times and instrument lights come on and car starts and runs fine. In the last 4 days I built a led code reader and ran codes, code 17 CPS keeps coming back, I've been told its possibly a bad EZL, or ignition switch, I've been told to check for voltage from ignition switch to EZL with a test light, dim light= bad ignition switch, not sure which wire has the voltage on EZL? so its been narrowed down between EZL and ignition switch, I don't think the CPS would disable all instrument lights? its been suggested that plastic ignition switch connector gets loose contacts, also I've been told brake light switch can cause issues?

I'm going to start testing today, a electrical schematic for power feed from switch to EZL would be handy! here's a video I made of issue, thanks John.
https://www.youtube.com/watch?v=uC9_7v7Ie5I

code 17 will always post if the car is not running. always seen it and after a few cars, i quit replacing them for that. a glitchy crank sensor will stall a car and never give a code for it. i have a test harness and scope them at the ezl.

the clusters are wonky but won't stall a car, replaced a few of those and 140s just 'cuz they act weird or go dead. a bad ignition switch can cause both stalling and cluster weirdness. given that i've replaced more sensors than ignition switches for stalling on those cars, i'd test that first.

you may have 2 or 3 problems, gotta wait for a real failure or test, test, test.

good luck, chuck.

Thanks, I just tested CPS cold 866ohms, this issue was so intermittent for months, could drive 2 weeks without it stalling, now it happens in my garage, so easier to diagnose, now going to test for voltage to EZL with ignition working hopefully, identify plug that has it, then with with ignition doing its no start thing. threw my back out Saturday pushing my car out of traffic, the joy.

resistance is futile-sorry, couldn't resist.

when i scope those things, i start the car, watch the wave, then close the hood to build heat. unless it's real fragile, it won't stall until it heats up. good luck, chuck.

John, please help us out a little here and put some periods in your paragraphs. Your first post is really hard to read and understand.

Your talking about the CPS right? I know they act up once heated, stall the car, let it cool off and car starts, I don't have a harness or scope, so to test it I was thinking of removing it ,and heating it up and take measurement to see if is bad.
So I just finished testing the power feed from ign switch to EZL, if it even go's there? anyways this is what I got, using my snap on test light detected nice bright light on 3 sockets with switch working & instrument lights working as it should, pin #1 #3 #6 have juice.
putting my key in and to position two a few times, issue surfaced, no ignition lights, only had bright light on pin #3.
Thoughts?

Sorry will do!

resistance tests will pass a bad sensor. once in a while it's a valid test. good luck, chuck.

What sensors should I look at?

the crank sensor is the only 1 i know that will stall a car. thought we went over that. good luck, chuck.

Did you replace the insulators behind the distributor caps? If not, get them swapped.

They are super clean, the whole car is clean never abused, it now has 37K on it.

This has been a nightmare problem for me, it all started when I replaced distributor caps 7 months ago, don't understand how that could make car just die and complete loss of voltage.

I installed Beru caps, returned them and got Bosch, also updated rotor bracket, still had problem.

Put my originals back in, still had issue.

Issue was so intermittent, could drive the car for weeks without it stalling, well now whatever it is, its doing it in my garage so it should be easier to find! but need a power flow schematic ,which I cannot find!

EZL's don't go out very often so not a lot of info out there! plus their super expensive!

Not sure if this could have caused issue, but the car needed a new Alternator and voltage regulator, running volts would go below 12VDC with any accessories on, mostly at idle.

This low voltage would stall the car because all the modules can not run without proper voltage!

I've heard of over voltage killing modules but thats what the OVP is for. installed a new one just in case.

I have issue narrowed down between EZL inputs and ignition switch, I have read a few posts that the electrical connector at ignition switch can get loose sockets causing issue, so going to check that out next.

How would I know this? on EZL #B 8 pin connector I get 12Volts on three sockets with normal start condition.

when its in the no start condition, no dash lights, cranks will not start, I get 12 volts only on one of those same sockets, so has to be ignition switch or something in between.

I've tried to trace #B 8 pin connector wires, but they go under fuse box and disappear, they may be going to a relay there? way in the back of fuse box there's a bunch of plug in relays, I need to find out what their for?

sorry for long post, this may be a simple issue, hope it is! for those with same issue and see this post I have a running post on Benzworld here.

https://www.benzworld.org/forums/r129-sl-class/2946761-strange-issue-flashing-dash-lights.html

Replace the insulators anyway

maybe i wasn't clear about 2 or 3 problems.

1-bad crank sensor
2-bad ignition switch and/or
3-bad cluster

bad igntion switch CAN cause stalling. the previous generations 107, 126, etc-very likely. it can also kill the cluster, too. if the ignition is on and the cluster is dead, does the ac blower work? can you wiggle the key-w/o turning it off-and things come to life? replace the ignition switch.

bad crank sensor CAN cause stalling. replaced alot of them over the years for just that.

the 129 and 140 clusters are known for acting weird on their own. there's no test for it, just observation. cluster going dead will not stall a car, in my experience.

as far as testing at the ezl, you need a wiring diagram and a volt meter to see where it's got power with key off and on. test lights won't say how MUCH voltage. i've got the diagrams but the printer's down and i cant decipher it on this screen. once you determine that, then you have to look at the crank sensor and the outputs to coils pin 1. coils pin 15 should have 12v with the key on. if the ezl is getting proper power and ground, the crank sensor is working, then the ezl fires the coils. if by chance, all is good but the ezl DOESN'T fire, that's the problem. VERY unlikely, unless the key has been left on for a long time-like hours-and it heated up and died. at 37k, i really doubt it. seen that design ezl go 200k and up and i've not replaced 1. seen a couple get replaced-it does happen. i wouldn't worry about the insulators-again, 37k.

is it all related? can't tell. at 37k, i can't believe that anything has failed. crank sensors need lotsa heat cycles to break down and ignition switches need lotsa key cycles to wear out. the cluster-maybe. but it won't fix your stalling problem. good luck, chuck.

I took the lower dash panel off to take a look see at wiring to ignition switch, oh boy looks like fun LOL.

When its in no start , no inst lights ,cranks condition, all HVAC functions are dead, along with both windows non opt, plus a super strange noise coming from rear view mirror, must be that temp aspirator fan.

I did test connector B at EZL for voltage, when car is in normal mode, I get 12v at sockets 1,3,6 , when its in no start condition, only get 12v on socket #3.

So problem seems to be ahead of EZL.

I just got a hold of StarTekinfo , this may help me figure it out!
http://manual.startekinfo.com/manual/JSP/model129.jsp